Apparatus for comminuting and dispersing solid particles

ABSTRACT

Apparatus for comminuting dry solid particles to a size of one micron or less comprises a vessel which contains a supply of balls agitated by one or more disks mounted on a shaft which is coaxial with and extends into the vessel. The comminuted material is evacuated by gravity or by conveying a gas through the interior of the vessel. The diameters of balls do not exceed 5 millimeters and the diameters of agitating disks are between 70 and 90 percent of internal diameter of the vessel.

United States Patent Kaspar et al. [451 Aug. 8, 1972 [54] APPARATUS FORCOMMINUTING 3,458,144 7/1969 Lessells ..241/46.02 AND DISPERSING SOLIDPARTICLES 3,486,705 12/ 1969 Szegvari ..241/ 172 [72] Inventors: JanKaspar, Pardubice; vladislav 3,223,336 12/1965 W1enert ..241/172 c il l:1 0f Pafdubice; FOREIGN PATENTS OR APPLICATIONS 380,298 11/1931 GreatBritain ..241/172 [73] Assignee: Vyzkumny Ustav Organickych Synv tez,Pardubice, Czechoslovakia Primary Examiner-Donald G. Kelly [22] Filed:March 25, 1969 Attorney-M1chael S. Striker [21] Appl.No.: 810,183 [57]ABSTRACT Apparatus for comminuting dry solid particles to a [52] US. Cl...241/50, 241/54, 241/172 Size of one micr n r l ss comprises a vesselwhich 51 1m, (:1 ..B02c 17/16 contains a pp y of balls agitated by oneor more 58 Field of Search ..241/4602, 47.50, 171, 172 disks mounted ona Shaft which is coaxial with and tends into the vessel. The comminutedmaterial is [56] References Cited evacuated by gravity or by conveying agas through the interior of the vessel. The diameters of balls do notUNITED STATES PATENTS e rceed 5 millimeters and the diameters ofagitating 3,243,128 3/1966 Tight ..241/172x ggfi fi ggjg z and 90 pe'cem3,311,310 3/1967 Engels ..24l/172X 3,337,140 8/1967 Wahl ..241/172 X 9Claims, 10 Drawing Figures SOURCE 0r 301/0 PAM/ms fa l'n/ef 40PATENTEDAUG 8 I972 sum: or 4 any. 2

WWW

52%] a] a] M Z};

INVENTOR In) :4 s 0M APPARATUS FOR COMMINUTING AND DISPERSING SOLIDPARTICLES BACKGROUND or THE INVENTION The present invention relates toimprovements in apparatus for comminuting and dispersing solidparticles. More particularly, the invention relates to improvements inapparatus of the class including so-called ball mills, stream mills andlike machines wherein dry solid particles are comminuted by balls oranalogous dispersing elements which are agitated in the interior of avessel. Still more particularly, the invention relates to improvementsin apparatus which are especially suited for breaking up solid granularor like material into minute particles with a size in the range of oneor more microns or a fraction of a micron. The definition breaking up isintended to embrace reducing the size of larger solid particles so thatthey yield smaller particles as well as separating agglomerations ofsmaller particles into a mass of discrete particles.

It was found that, once the material which is treated in conventionalball mills -or analogous apparatus reaches a certain degree of fineness,no further refinement takes place even if the material remains in theapparatus for extended periods of time. Reference may be had, forexample, to German Pat. Nos. 589,796, 592,105 and 642,127 which disclosesuch types of apparatus. It was further found that the time required toreduce the size of solid particles in conventional apparatus, especiallyif the particles are to be converted into a mass of finely comminutedmaterial, is very long so that the operation of such apparatus isuneconomical. This is attributed to the fact that conventional apparatusutilize relatively large balls or analogous dispersing elements,normally with a diameter of about 20 millimeters. If such balls are usedto break up particles to a size of about 0.001 millimeter, the ratio ofthe size of particles of the ultimate product to the size of the ballsis about 120,000; therefore, the probability of satisfactory impact ofcomminuted material against the balls depends too much on the roughnessof external surfaces of balls and on the speed at which the balls areagitated in the interior of the vessel, i.e., on frequency of impact ofballs against one another. As a rule, the device which agitates theballs cannot be rotated at a speed which exceeds a predetermined value.It was further found that, in conventional apparatus, the efficiencydoes not depend on the energy of collisions between particles ofcomminuted material and the balls. The comminuting action is terminatedwhen the comminuted particles cease to move with reference to each otherand with reference to the balls. Some but not all of the aboveenumerated problems are eliminated when the dispersing elements fillonly a certain portion of the interior of the vessel.

SUMMARY OF THE INVENTION It is-an object of the invention to provide anovel and improved apparatus which is capable of comminuting solidparticles to a size of one micron or less in a timesaving operation.

Another object of the invention is to provide an apparatus which canbreak up agglomerations of coherent particles or which can be used tobreak up discrete solid particles in a small area, faster than inconventional apparatus, and with a higher degree of efficiency.

A further object of the invention is to provide the apparatus with novelagitating means for balls or analogous dispersing elements.

Our invention is based on the recognition that the dispersing elementscan comminute solid particles with greater efficiency and moreeconomically if the mixture of solid particles and dispersing elementsis agitated at a high speed, if the ratio of maximum dimensions ofdispersing elements to. maximum dimensions of admitted solid particlesis less than in conventional apparatus, and if the dispersing elementsand solid particles are maintained in motion by novel agitating means.The agitating means is designed in such a way that the entire contentsof the vessel are kept in constant motion and that the contents of thevessel fill the latter when the apparatus is in use even though thecombined volume of solids is substantially less than the capacity of thevessel when the apparatus is idle.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved apparatus itself, however, both as to its construction and itsmode of operation, together with additional features and advantagesthereof, will be best understood upon perusal of the following detaileddescription of certain specific embodiments with reference to theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partly schematic and partlyvertical sectional view of a dispersing and comminuting apparatus whichembodies one form of our invention;

FIG. 2 is a fragmentary schematic sectional view of a second apparatus;

FIG. 3 is a fragmentary schematic sectional view of a third apparatuswhich constitutes a modification of the apparatus shown in FIG. 2;

FIG. 4 is a fragmentary schematic sectional view of a fourth apparatuswhich is similar to the apparatus of FIG. 3;

FIG. 5 is a fragmentary schematic sectional view of a fifth apparatuscomprising a rotary separator which is built into its vessel;

FIG. 6 is a fragmentary schematic sectional view of a sixth apparatuswhich comprises an externally mounted separator;

FIG. 7 is a fragmentary schematic sectional view of a seventh apparatuswhich constitutes a modification of the apparatus shown in FIG. 6;

FIG. 8 is a schematic partly sectional and partly elevational view of afurther apparatus with two externally mounted separators;

FIG. 9 is a schematic sectional view of a multi-stage separator whichcan be utilized in the apparatus of FIGS. 1 to 8; and

FIG. 10 is a similar schematic sectional view of a modified multi-stageseparator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. I,there is shown an apparatus which comprises a horizontal cylindricalvessel or container l which contains a supply of dispersing elements 30.Such dispersing elements (hereinafter called balls for short) may be ofspherical, ovoid, polygonal or other regular or irregular shape and arekept in motion by agitating members 5 mounted on a horizontal driveshaft 4 which is coaxial with the vessel 1. Particles of sand can beused as dispersing elements. The shaft 4 extends through a stuffing box31 in the left-hand end wall 2 of the vessel 1 and is joumalled inbearings 32, 33 provided in brackets 34, 35 carried by a base member 36.The left-hand end of the shaft 4 is fixed to a pulley 37 which is drivenby an electric motor or another suitable prime mover through theintermediary of V-belts, not shown. The vessel 1 is provided with aninlet 6 which is adjacent to the end wall 2 and serves to admit drysolid particles which are comminuted in the chamber 1a of the vessel andare thereupon evacuated by way of an outlet 8 adjacent to the right-handend wall 3 of the vessel. A screen or filter 9 of fine mesh is installedin the outlet 8 to confine the balls 30 in the chamber 1a. Since thedispersed material is evacuated upwardly (by way of the outlet 8), thevessel 1 is preferably further provided with a second inlet 7 whichadmits a gas serving as a carrier to entrain comminuted particlesthrough the interstices of the filter 9 and upwardly through the outlet8. The inlet 7 is connected to a source 38 of compressed fluid, e.g.,air or an inert gas (such as nitrogen).

The vessel 1 includes a jacket 39 provided with an inlet 40 and anoutlet 41. The compartment defined by the jacket 39 serves toaccommodate circulating heating or cooling fluid (gas or liquid) if andwhen a heating or cooling of solid particles is necessary. If the fluidentering at 40 is a heating medium, the apparatus further comprises aheat exchanger 42 which maintains the circulating medium at a desiredtemperature. The vessel 1 (or the gas which is admitted by way of inlet7) is cooled if the particles admitted through the inlet 6 are soft atroom temperature or when the treatment at room temperature or above roomtemperature would adversely affect the color, quality or othercharacteristics of treated material.

The mixture of balls 30 and solid particles preferably fills between 40and 85 percent of the chamber 10. The volumetric ratio of balls 30 tosolid particles in the chamber la is between 0.3 and to one, preferablybetween two and 10 to one, i.e., the volume occupied by balls ispreferably a multiple of the volume occupied by solid particles. Theremaining part of the chamber 10 (namely, between and 60 percent) isfilled with gas. When the shaft 4 is idle, the chamber 1a accommodatesthree layers including a lower layer of balls 30, a median layer ofsolid particles, and an upper layer of gas. Of course, finer solidparticles penetrate into the gaps between the balls in the lower layer.When the shaft 4 is rotated at a high speed, the gas, solid particlesand balls 30 form a homogeneous mixture which fills the entire chamberla.

The means for feeding solid particles from a hopper 43 or anothersuitable source to the inlet 6 may comprise a screw conveyor 44 or thelike. The conduit connecting the source 38 with the inlet 7 preferablyaccommodates an adjustable pressure regulating valve 45 so that theoperator can select the rate of admission and pressure of the gaseouscarrier as a function of the speed of comminuted particles which are tobe evacuated through the interstices of the filter 9.

For example, the apparatus of FIG. 1 may employ a vessel 1 having aninternal diameter of 300 millimeters and an axial length of 420millimeters, a total of seven agitating members 5 each having a diameterof 260 millimeters, and the distance between adjoining agitating membersmay be 60 millimeters. The valve 45 may be adjusted to admit gas at therate of 10 cubic meters per hour. The pressure of gas which is admittedvia inlet 7 need not be high. Such gas must overcome the resistance ofthe filter 9 and the resistance of filter or filters (to be described inconnection with FIGS. 8 to 10) which are used to separate the gaseouscarrier from finely comminuted material. As a rule, and particularlywhen the outlet discharges comminuted material downwardly, thecomminuting and dispersing operation is carried out at normal pressure.Nitrogen or another inert gas is employed when the apparatus is used inan area where an explosion is likely to occur or when the material to becomminuted should not be mixed with oxygen.

The interstices of the filter 9 should be small enough to prevent escapeof freshly introduced solid particles and/or the escape of balls 30. Itis normally sufficient if the size of interstices in the filter is about50 percent of the size of particles which are admitted by way of theinlet 6. The filter 9 may be a sheet of textile material or a sheetwhich is formed with slits or other types of openings. The size ofparticles which are admitted from the source 43 is preferably less than500 microns, most preferably between and 300 microns or even less than100 microns. The fineness of comminuted material depends on the grindingtime; the size of particles which are evacuated by way of the outlet 8may be in the range of one micron or even less than one micron. Thegrinding time is variable and depends on the desired size of finelycomminuted material. Such grinding time may vary between one or moreminutes and one or more hours. In normal operation, the contents of thechamber la are maintained at or slightly above room temperature, forexample, at 30 C, provided that the material admitted via inlet 6 issolid at such temperature.

If desired or necessary, the apparatus may be mounted in such a way thatthe common axis of the shaft 4 and vessel 1 is inclined with referenceto a horizontal plane. The angle of inclination with reference to suchhorizontal plane is preferably less than 60, most preferably less than45.

The ability of our apparatus to produce a stream of finely comminutedparticles with a size in the range of one micron or less is attributedto the fact that we prefer to utilize relatively small balls oranalogous dispersing elements 30. At the present time, we prefer toutilize dispersing elements having a maximum transverse dimension in therange of 0.1 to 5 millimeters, most preferably between 1-5 millimeters.As a rule, the ratio between the maximum dimensions of dispersingelements and the maximum dimensions of freshly admitted solid particlesis between 10:1 and 10,000z1. A very satisfactory ratio is between 100:1and 1,000zl. The motor or other prime mover which rotates the shaft 4 ispreferably of the variable-speed type so that the speed of the agitatingmembers 5 can be varied within a wide range. The rotational speed ofthese agitating members is preferably high to insure an intensivedispersing and comminuting action which results from repeated collisionbetween the balls 30 and the solid particles. The fact that the mass ofdispersing elements is relatively small does not affect the quality ofdispersing and comminuting action. The dispersing speed is proportionalto the frequency and intensity of collisions between the balls 30 andsolid particles; the factors which afiect such dispersing speed includethe dimensions of balls 30, the ratio of the combined volume of balls 30to the combined volume of solid particles in the chamber In, the ratioof the combined volume of balls 30 and solid particles to the volume ofthe chamber 1a, the specific weight of balls 30, the specific weight ofsolid particles, the size of solid particles which are admitted viainlet 6, and the size of comminuted material which is evacuated by wayof the outlet 8. The ratio of specific weight of the balls 30 tospecific weight of solid particles is normally between 0.1 and 8 to one.The nature of the material of the balls 30 depends on the nature ofsolid particles. Such material may be glass, ceramic, metal or plastic,e.g., polyvinyl chloride, polystyrene, Teflon (trademark) and/or others.

Another feature of our apparatus which contributes significantly tointensive dispersing and comminuting action resides in that thedimensions of agitating members are in a certain relationship todimensions of the vessel 1. It was found that the diameters of agitatingmembers 5 should be less than the diameter of the cylindrical internalsurface of the vessel 1, preferably between 70 and 90 percent of suchinternal diameter. It was further found that, if the apparatus employstwo or more agitating members, the axial distance between such agitatingmembers should preferably correspond to between 20 and 50 percent oftheir diameter. The agitating members 5 preferably resemble orconstitute disks which are provided with slots, holes or analogousrecesses or openings and/or with ribs or other protuberances to insuresatisfactory entrainment of balls 30 and solid particles when the driveshaft 4 rotates. It was found that disk-shaped agitating members undergolittle wear, even at very high speeds in the range of 5-30 meters persecond which are desirable to bring about satisfactory agitation of thecontents of the chamber 11.

The apparatus can be operated continuously or intermittently and may beemployed for comminuting and/or dispersing of different sizes and/ortypes of solid particles. The valve 45 may be closed to seal the inlet 7from the source 38 if the nature of solid material is such that it canbe evacuated without resorting to a gaseous carrier. As will beexplained hereinafter, the gaseous carrier which is discharged by way ofthe outlet can be recirculated through the chamber 1a. Furthermore, atleast those parts of the apparatus which are subjected to extensive wearcan be provided with one or more coats or layers of highlywear-resistant material.

FIG. 2 illustrates schematically certain details of a modifiedapparatus. The main difference between the apparatus of FIGS. 1 and 2 isthat the latter does not employ a gaseous carrier, chiefly because theoutlet 108 is arranged to discharge comminuted material downwardly sothat such material can be evacuated by gravity. All such parts of themodified apparatus which are clearly identical with or analogous tocorresponding parts of the apparatus shown in FIG. 1 are denoted bysimilar reference numerals plus 100. The chamber of the vessel 101accommodates a transverse partition 10 at least a portion of whichconstitutes a filter or sieve to provide interstices for passage offinely comminuted material which is thereupon caused to leave the vesselby way of the outlet 108. The partition 10 may form an integral part ofthe end wall 103 which is preferably detachably secured to thecylindrical shell of the vessel 101. In the embodiment of FIG. 2, thefilter or sieve constitutes the upper part of the partition 10. Thispartition may consist of sheet metal which is formed with slits, roundholes or other types of interstices for passage of finely comminutedmaterial. When the shaft 104 rotates, the balls (not shown) cooperatewith the agitating members 105 to automatically transport finelycomminuted material from the inlet 106 toward the partition 10.

FIG. 3 shows a portion of a third apparatus wherein all such parts whichare clearly identical with or analogous to the parts of the apparatusshown in FIG. 1 are denoted by similar numerals plus 200. The inlet 206for solid particles is provided in the upper portion of the end wall 203and the outlet 208 for finely comminuted material is located in thelowermost part of shell of the vessel 201 adjacent to the end wall 202.In this apparatus, the filter 9 or 10 is replaced by another confiningdevice which prevents escape of dispersing elements and freshly admitted(non-communited) solid particles from the chamber of the vessel 201.This confining device comprises a ring 12 which is installed in thechamber of the vessel 201 and extends a relatively short distance towardthe shaft 204, and a disk 11 which preferably constitutes the leftmostagitating member and defines with the adjoining end face of the ring 12a narrow annular gap or an annulus of discrete gaps through which finelycomminuted material is free to pass on its way toward the outlet 208. Itwill be seen that the gap or gaps for evacuation of communited materialare defined by stationary and moving parts 12, 11.

The only important difierence between the apparatus of FIGS. 3 and 4 isthat the latter comprises a stationary ring 312 which is adjacent to theinner side of the disk 311, i.e., the disk 311 is located between thering 312 and the end wall 302. All other parts of the apparatus shown inFIG. 4 are denoted by numerals similar to those employed in FIG. 3 plus100. An advantage of the apparatus shown in FIG. 4 is that finelycomminuted material passes through the gap or gaps between the parts311, 312 under the action of centrifugal force.

In the apparatus of FIG. 5, the means for confining dispersing elementsand freshly admitted solid particles in the chamber of the vessel 401comprises a rotary separator 13 which is preferably (but notnecessarily) installed in the end wall 403 and is driven by the shaft404 or by a separate drive 13a (indicated by phantom lines). Theseparator 13 comprises a preferably conical rotor 13b which defines anarrow annular gap with a stationary tube 13c for passage of finelycomminuted material into the outlet 408. The latter can form an integralpart of the tube 130. The separator 13 can perform the additionalfunction of separating coarser and finer particles of the material whichenters the tube 13c. All other parts of the apparatus of FIG. 5 aredenoted by numerals similar to those employed in FIG. 1 plus 400.

The apparatus of FIG. 6 constitutes a further modifi cation of theapparatus shown in F IG. 1. This apparatus comprises a separator 14which is mounted externally of the vessel 501. The outlet 508 for finelycomminuted material is formed with a perforated wall and extends intothe separator 14 to receive the gaseous carrier and the finelycomminuted material. All coarserparticles are returned into the chamberof the vessel 501. The parts 502-507 correspond to parts 2-7 of theapparatus shown in FIG. 1.

FIG. 7 shows an apparatus wherein the separator 15 for gaseous carrierand comminuted material is mounted on the cylindrical shell of thevessel 601. The outlet 608 evacuates comminuted material. Coarserparticles are returned into the vessel 601. The parts 602-607 correspondto parts 2-7 of the apparatus shown in FIG. 1.

FIG. 8 illustrates schematically an apparatus wherein the gaseouscarrier is recirculated through the chamber of the vessel 701. Theapparatus comprises two separators 16, 17 the first of which separatescomminuted material and gas from dispersing elements and coarser solidparticles and the second of which separates comminuted materials fromthe gaseous carrier. The separator 16 comprises a rotor 16a which isprovided with a filter or sieve (e.g., a textile filter) havinginterstices just large enough to permit entry of gas and comminutedmaterial into a conduit 1612 which admits the mixture of gas andcomminuted material into the housing 170 of the second separator 17.This housing accommodates a rotor 17a which is designed to retaincomminuted solid material but to permit entry of gaseous carrier into aconduit 17b connected to the intake of a blower 18. The pressure side ofthis blower is connected with the inlet 707 of the vessel 701. Solidparticles which cannot penetrate through the rotor 16a of the firstseparator 16 leave the latters housing 160 by way of a return conduit16d which discharges its contents through the end wall 703 and back intothe chamber of the vessel 701. The outlet 708 for comminuted material isprovided in the bottom portion of the housing 17c. The efficiency(separating action) of separators 16, 17 depends on the size ofinterstices in their rotors 16a, 17a and on rotational speed of suchrotors. Each of these rotors can be driven by a pulley or the like, notshown, preferably from a variable-speed motor or transmission. The samemotor or transmission can also serve to drive the rotor of the blower l8and to rotate the drive shaft 704 for the agitating members 705. Thenumerals 702,706 respectively denote the left-hand end wall of thevessel 701 and the inlet for solid particles. As described in connectionwith and as shown in FIG. 1, the vessel of the apparatus can be heatedor cooled, depending on the nature of solid particles and/or on certainother factors. It is also possible to employ in the apparatus of FIG. 8(or in the apparatus of FIG. 1 or 6 or 7) a vessel which does not have acooling or heating jacket and to provide instead a heat exchanger (shownat l7e in FIG. 8) which heats or cools the gaseous carrier upstream ordownstream of the blower. I

It is further clear that the separator 16 and/or 17 of FIG. 8 can bereplaced by other types of separators without departing from the spiritof our invention. For example, the apparatus can employ a bag filter, a

chamber filter or the like. Furthermore, the separators 16, 17 of FIG. 8can be replaced by a multi-stage separator of the type shown in FIG. 9.This separator is designed to segregate coarse solid particles anddispersing elements from gases and comminuted material and to thereuponseparate comminuted material from gases. The mixture of solid particles,comminuted material and gaseous carrier is admitted by suction into anouter housing 19a by way of an inlet 19. The housing 19a accommodates anupright hollow rotary outer filter 24 having interstices large enough topermit passage of gases and comminuted material into the interior ofthis filter. The solid particles which are too large are intercepted bythe filter 24 and descend by gravity into an outlet 20 which returnsthem into the vessel, not shown. The mixture of gases and solidcomminuted material is separated in the interior of the outer filter 24;thus, the gases are drawn into a pipe 22 through the interstices of ahollow rotary inner filter 23 which is coaxially mounted in the outerfilter 24. The filter 23 intercepts the comminuted material whichdescends by gravity into an outlet 21 corresponding to the outlet 8 inthe apparatus of FIG. 1. The numberals 25, 25a respectively denote gearswhich form part of two independent drives for the filters 23, 24, i.e.,each of these filters can be rotated at a different speed. The upperportions of filters 23, 24 rotate in antifriction gearings 26, 26a. Itis also possible to rotate the filters 23, 24 in different directions.

FIG. 10 illustrates a modified multistage separator. All parts of thisseparator which are clearly identical with or analogous to the parts ofthe separator shown in FIG. 9 are denoted by similar reference numeralsplus 800. The main difference is that the filters 823, 824 are rigidlyconnected to each other so that they rotate at the same speed and in thesame direction. The pipe 822 for the gaseous carrier can form part ofthe drive which rotates the filters 823, 824.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featureswhich fairly constitute essential characteristics of the generic andspecific aspects of our contribution to the art.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:

1. Apparatus for comminuting and dispersing solid particles to form amass of finely comminuted solid material, said apparatus comprising avessel having an internal chamber provided with inlet means foradmission of solid particles and outlet means for evacuation ofcomminuted material; agitating means comprising a drive shaft extendinginto said chamber and at least one substantially disk-shaped agitatingmember provided on said drive shaft in the interior of said vessel; asupply of discrete dispersing elements in said chamber, said elementsbeing arranged to move in response to rotation of said agitating meansto thereby convert solid particles admitted through said inlet meansinto finely comminuted material; a source of compressed gas; and secondinlet means for admitting gas from said source into said chamber so thatthe thus admitted gas carries comminuted material toward and into saidoutlet means.

2. Apparatus as defined in claim '1, wherein said vessel comprises acylindrical internal surface and wherein said shaft is coaxial with saidvessel.

3. Apparatus as defined in claim 2, wherein the diameter of saiddisk-shaped agitating member is and percent of the diameter of anagitating member.

6. Apparatus as defined in claim 1, wherein said outlet means isarranged to discharge comminuted material and gases upwardly from saidchamber.

7. Apparatus as defined in claim 1, wherein the maximum dimensions ofsaid dispersing elements are in the range of between 0.1 and 5millimeters.

8. Apparatus as defined in claim 1, further comprising confining meansfor retaining the dispersing elements and solid particles whose sizeexceeds a predetermined value in said chamber.

9. Apparatus as defined in claim 8, wherein said confining meanscomprises a filter in the region of said outlet means.

1. Apparatus for comminuting and dispersing solid particles to form a mass of finely comminuted solid material, said apparatus comprising a vessel having an internal chamber provided with inlet means for admission of solid particles and outlet means for evacuation of comminuted material; agitating means comprising a drive shaft extending into said chamber and at least one substantially disk-shaped agitating member provided on said drive shaft in the interior of said vessel; a supply of discretE dispersing elements in said chamber, said elements being arranged to move in response to rotation of said agitating means to thereby convert solid particles admitted through said inlet means into finely comminuted material; a source of compressed gas; and second inlet means for admitting gas from said source into said chamber so that the thus admitted gas carries comminuted material toward and into said outlet means.
 2. Apparatus as defined in claim 1, wherein said vessel comprises a cylindrical internal surface and wherein said shaft is coaxial with said vessel.
 3. Apparatus as defined in claim 2, wherein the diameter of said disk-shaped agitating member is between 70 and 90 percent of the diameter of said chamber.
 4. Apparatus as defined in claim 2, wherein the angle of inclination of the common axis of said shaft and said vessel with reference to a horizontal plane does not exceed 45 degrees.
 5. Apparatus as defined in claim 1, wherein said agitating means comprises a plurality of agitating members spaced from each other in the axial direction of said shaft by distances corresponding to between 20 and 50 percent of the diameter of an agitating member.
 6. Apparatus as defined in claim 1, wherein said outlet means is arranged to discharge comminuted material and gases upwardly from said chamber.
 7. Apparatus as defined in claim 1, wherein the maximum dimensions of said dispersing elements are in the range of between 0.1 and 5 millimeters.
 8. Apparatus as defined in claim 1, further comprising confining means for retaining the dispersing elements and solid particles whose size exceeds a predetermined value in said chamber.
 9. Apparatus as defined in claim 8, wherein said confining means comprises a filter in the region of said outlet means. 